1. Field of the Invention
The present invention relates to a liquid crystal display (xe2x80x9cLCDxe2x80x9d) panel having electrostatic discharge (xe2x80x9cESDxe2x80x9d) prevention circuitry for reducing static electricity. In particular, it relates to an LCD panel having ESD prevention circuitry that allows testing of the panel during manufacturing as well as normal operation of the panel thereafter.
2. Discussion of the Related Art
During the fabrication process of an LCD panel, high voltages often develop, such as by friction or discharge, across various electrical components of the panel. Such high voltages may generate instant currents that flow through the wires, the intersections of the wires, and the thin film transistors (xe2x80x9cTFTsxe2x80x9d) formed on the LCD panel. This causes defects and malfunctions in the panel such as an electrical short or open. It is therefore desirable to reduce or eliminate static electricity especially during the manufacturing process of the LCD panel.
FIG. 1 shows a prior technique for static electricity prevention. An LCD panel includes a plurality of intersecting gate lines G1 to GN and data lines D1 to DM. Each of the gate lines G1 to GN is connected at a first end to a gate driving circuit 2 which provides gate signals for the LCD panel, and each of the data lines D1 to DN is connected at a first end to a data driving circuit 4 which provides data signals for the LCD panel. The intersecting gate and data lines define a pixel array or matrix. At each intersection of a gate line and a data line, a pixel element comprising a TFT 10 and a pixel electrode 12 is electrically coupled to the gate and data lines.
Each of the data lines D1 to DM and the gate lines G1 to GM is electrically coupled at a second end to a common shorting bar SB. During fabricating, electrostatic discharge is reduced or prevented because the common shorting bar SB shorts the gate and data lines. The common shorting bar, however, may interfere with the testing of the LCD panel during manufacturing as well as the intended normal operation of the panel, both of which require voltage differences to be applied across the data and gate lines. Thus, this ESD prevention technique requires an additional step of removing the shorting bar after the LCD panel is formed.
FIG. 2 shows another prior technique for static electricity prevention. Identical components in FIGS. 2 and 1 are designated by identical reference symbols. In this device, a transistor 14 is electrically coupled between the common shorting bar SB and the second end of each of the data lines D1 to DM and gate lines G1 to GN. The two gate electrodes of the CMOS transistor 14 are coupled to the data or gate line and the common shorting bar, respectively. The transistors 14 act as diodes. When a voltage is applied to the data or gate line due to static electricity, the transistor 14 is turned on to allow a current to flow between the data or gate line and the common shorting bar SB through the current path of the transistor. This reduces the voltage difference across the transistor 14 until the gate voltages are sufficiently low that the transistor is turned off. Since all data and gate lines are coupled to the common short bar SB via transistors, ESD is reduced or prevented during the fabricating process.
However, during panel testing and normal operations of the LCD panel, the transistors 14 may be turned on, and the signals on the data and gate lines may become distorted due to the currents that flow between the gate lines and the data lines through the transistors, which have low turn-on resistance.
Accordingly, the present invention is directed to an LCD panel having ESD prevention circuitry that substantially obviates one or more of the problems due to limitations and disadvantages of the prior technique and related art.
An object of the present invention is to provide an LCD panel having ESD prevention circuitry by using switching devices.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display panel for static electricity prevention includes a plurality of gate lines from a gate driver and a plurality of data lines from a data driver, the gate lines and data lines forming a pixel array, a switching device and a pixel electrode are connected electrically to each pixel, a plurality of static electricity prevention circuits having at least one switching device, each static electricity prevention circuit connected to ends of the gate line and the data line; a common wire connected to each static electricity prevention circuit, the common wire coupling the gate lines with data lines in common; and at least one control part connected to each static electricity prevention circuit, the control part generating a control signal which turns off the switching device.
In another aspect of the present invention, a liquid crystal display panel having electrostatic discharge prevention circuitry comprises a plurality of gate lines; a plurality of data lines, the gate lines and the data lines define an array of pixels; a plurality of switching devices respectively connected to the pixels, the switching devices connected to the gate lines and data lines; a common line; and a plurality of electrostatic discharge prevention circuits each coupled to the common line and one of the gate and data lines, each electrostatic discharge prevention circuit having at least one switching device and at least one control terminal connected to the at least one switching device, wherein the at least one switching device operates in response to a signal from the control terminal.
In another aspect of the present invention, a method for making a liquid crystal display panel having electrostatic discharge prevention circuitry comprises the steps of forming a plurality of gate lines; forming a plurality of data lines, the gate lines and the data lines defining an array of pixels; forming a plurality of switching devices respectively connected to the pixels, the switching devices connected to the gate lines and data lines; forming a common line; and forming a plurality of electrostatic discharge prevention circuits each coupled to the common line and one of the gate and data lines, each electrostatic discharge prevention circuit having at least one switching device and at least one control terminal connected to the at least one switching device, wherein the at least one switching device operates in response to a signal from the control terminal.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.